Many observers claimed that the by-election that took place on October 26 would not only determine the new mayor of Seoul, but would also forecast the results of next year’s presidential election. In order to further analyze the by-election results, the Asan Institute for Policy Studies conducted an exit poll to investigate why and how voters cast their ballots. Previous exit polls only predicted who would win the presidential election. Our survey differs from past exit polls because we examine in detail voters’ rationale for supporting a particular candidate. Using alternative questions and methodology, we believe that our survey results will help shed more light on voters’ behavior and decision making processes.